بررسی اثرات گابا بر رشد و عملکرد کمی و کیفی گیاه شنبلیله تحت شرایط تنش کم آبی

Introduction
One of the most important climatic factors that affect the distribution of plants around the world and can cause morphological, physiological, and biochemical changes in the plant is the lack of water available to the plant. Water stress is actually one of the most important environmental stresses that can severely affect plant growth and performance. The mechanism of resistance to drought stress, in turn, differs among plant species. Therefore, plants have the ability to reduce the use of their resources and regulate their growth to cope with adverse environmental conditions such as drought. Stomatal regulation of plants through increasing ion transport, and abscisic acid signaling is also in the molecular mechanisms of plant response to drought stress. It is involved. One of the most efficient mechanisms of plants, when faced with water stress, is the osmotic regulation mechanism that occurs in plants in order to maintain turgescence and cell swelling.
Considering that the effect of GABA in inducing resistance to all kinds of stresses in plants is significant and the research in this field is increasing in the world, This research in Iran is still in its initial stages. Therefore, the present study was conducted with the aim of investigating the effects of GABA on the quantitative and qualitative growth and yield of basil and fenugreek under water stress conditions.
Considering the significant role of gamma-aminobutyric acid (GABA) in inducing resistance to various stresses in plants and the increasing research in this field globally, it is important to explore the effects of GABA on the quantitative and qualitative growth and yield of basil and fenugreek under water stress conditions in Iran.

Methodology
This research was carried out as a field and as a factorial experiment in the form of a randomized complete block design with three replications. For this purpose, 27 x 1.5 meter plots were prepared for each plant. 5 rows were placed in each plot and 7 seeds were placed in each row. After sufficient initial growth and seedling establishment, the first stage of GABA spraying (0, 1, and 2 mg/liter) was done. After about a week passed from the first phase of foliar spraying, water scarcity stress (irrigation at 100% (control), 75%, and 50% of the agricultural capacity of the field) was applied. The irrigation method applied in this research was closed-end irrigation, where water was provided to the roots using the plots created in the field and inside the experimental plots. Water entered the experimental plots through a 1-inch hose from the irrigation piping of Miandoab University. Irrigation treatment at three irrigation levels up to 100% of crop capacity as a control treatment. Irrigation of the land was applied until reaching 75% of the agricultural capacity and irrigation up to 50% of the agricultural capacity. Before each irrigation, the soil moisture was read using a hygrometer at a depth of 30 cm. According to the average amount of water required for irrigation control treatments, the volume of water for other treatments was determined by considering 25% and 50% reduction. Two weeks after the last stage of foliar spraying with GABA treatment at concentrations of 0, 1, and 2 mg/liter, morphological characteristics such as the number of side branches, plant length, pod length, pod diameter, pod number, and seed number per plant and the quantitative and qualitative yield of fenugreek was measured.
Chlorophyll and carotenoids were measured using the method (Arnon, 1949). To measure the amount of chlorophyll and carotenoids, 0.2 g of the fresh leaves of the plant were ground in a Chinese mortar containing 2 mL of 80% acetone, so that the chlorophyll enters the acetone solution, and then about 2 mL of the extract the obtained acetone was removed. The obtained acetone extract solution was centrifuged for 10 minutes at 4000 revolutions and then the optical absorption of the supernatant solution was read at wavelengths of 470, 646, and 663 by a spectrophotometer.
Folin Ciocalto reagent was used to measure total phenol compounds (Slinkard and Singleton, 1997). To perform this test, two mL of Fulin Ciocalto reagent was added to 400 µL of the diluted extract, and after five minutes, 1.6 mL of 75 g.L-1 sodium carbonate solution was added to it. After half an hour, the absorbance value of the mixture at 765 nm wavelength was read by a spectrophotometer in front of the blank. Different concentrations of calic acid were used to draw a standard curve. A spectrophotometer was used to measure flavonoids using the method of Krizek et al. (1998). The method of Miloskos et al. was used to measure the total antioxidant.
Data collection included measurements of plant height, leaf area, chlorophyll content, number of branches, fresh and dry weight of shoots and roots, and yield components such as number of seeds per plant, seed weight, and seed germination rate. Statistical analysis was performed using analysis of variance (ANOVA) and means were compared using Duncan's multiple range test. In the end, the data obtained from this experiment were analyzed with SAS 9.1 statistical software, and the averages were compared using Duncan's test at the probability level of 5%. Also, the graphs were drawn using Excel software.

Conclusion
In conclusion, the findings of this study demonstrate the positive effects of GABA application on the growth and yield of basil and fenugreek under water stress conditions. GABA-treated plants exhibited enhanced growth parameters and improved yield components compared to the control group. These results highlight the potential of GABA as a promising tool for mitigating the negative impacts of water stress on plant growth and productivity. Further research is warranted to explore the underlying mechanisms of GABA-induced stress tolerance in plants and its potential applications in agricultural practices.
The results of the research showed that the morphological and functional characteristics of fenugreek plants are directly affected by irrigation stress, and the use of GABA foliar application moderates the effects of irrigation stress in studied plants. One of the reasons for the decrease in the number of seeds in the pod can be related to insufficient photosynthesis and the production of the necessary materials for the growth of all the seeds due to water stress, which ultimately causes a smaller number of seeds to grow in the pod. As an additional result, the use of GABA foliar spray treatment with a concentration of 2 mg.L-1 under irrigation stress conditions has increased the content of phenol, flavonoid, and total sugar.